FWIW, ATF does not have a registry. My definition of a registry is a database that can be queried for responses on demand. Like a spreadsheet, but capable of being searched by name, or date, or type of weapon. The ATF has none of that.

What the ATF does have in its out of business record center are a mountain of paper Form 4473's from closed dealers and manufacturers, and then even more of those that were scanned into microfiche. Microfiche is simply a film image of a paper record. There is no index. You have to manually search it just like paper, by looking at each page. ATF stores microfiches records by dealer, and then by date. These are not searchable by name, date or any other keyword.